#include<sys/stat.h>
#include<stdlib.h>

int main(void)
{
	struct stat statbuf;

	//turn on set-group-id and turn off group-execute
	if(stat("foo", &statbuf) < 0)
		err_sys("stat error for foo");
	if(chmod("foo", (statbuf.st_mode & ~S_IXGRP) | S_ISGID) < 0)
		err_sys("chmod error for foo");

	//set absolute mode to "rw-r--r--"
	if(chmod("bar", S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) < 0)
		err_sys("chmod error for bar");

	exit(0);
}


